Modulation of an immune or inflammatory response can be a valuable tool in controlling various kinds of diseases including autoimmune diseases, diseases characterized by abnormal inflammation and/or immune response, and infections. In treating diseases characterized by abnormal inflammation and/or immune responses, such as inflammatory bowel diseases and autoimmune or inflammatory diseases, down-modulation of an immune response is desirable. In other situations, for example when vaccinating a patient to impart immunity to an infectious disease, stimulation of an immune response is desirable. In the vaccine setting, adjuvants that can heighten an immune response to a coadministered antigen can be valuable in providing long term protection against disease. Particularly lacking in the art are adjuvants capable of stimulating a mucosal immune response. A mucosal immune response, as opposed to a systemic immune response, is valuable because it can attack an infection at a very common point of entry, that is, at a mucosal surface. The present invention addresses these needs in the art by providing therapeutic agents to diagnose and treat diseases characterized by inappropriate and/or abnormal inflammation and/or immune responses and therapeutic agents that can act as adjuvants to stimulate an immune response, particularly a mucosal immune response.